查询各科成绩都大于80分的学生成绩

成绩表 score

stuname   subjectname   score

A         语文                 70

A         数学                 80
A         英语                 90
B         语文                 65
B         数学                 50
B         英语                 100
C         语文                 70
C         数学                 78

C         英语                 65

select * from score where stuname not in( SELECT stuname  FROM `score` where score<=80 GROUP BY stuname ,subjectname );

查询各科平均成绩不低于80分的学生的平均分

select stuname, AVG(score) avgscore from score GROUP BY stuname having AVG(score) >=80;